Blue laser

A blue laser is a laser that emits electromagnetic radiation with a wavelength between 360 and 480 nanometres, which the human eye sees as blue or violet. A blue laser is a laser that emits electromagnetic radiation with a wavelength between 360 and 480 nanometres, which the human eye sees as blue or violet. Blue beams are produced by helium-cadmium gas lasers at 441.6 nm, and argon-ion lasers at 458 and 488 nm. Semiconductor lasers with blue beams are typically based on gallium(III) nitride (GaN; violet color) or indium gallium nitride (often true blue in color, but also able to produce other colors). Both blue and violet lasers can also be constructed using frequency-doubling of infrared laser wavelengths from diode lasers or diode-pumped solid-state lasers. Diode lasers which emit light at 445 nm are becoming popular as handheld lasers. Lasers emitting wavelengths below 445 nm appear violet (but are sometimes called blue lasers). Some of the most commercially common blue lasers are the diode lasers used in Blu-ray applications which emit 405 nm 'violet' light, which is a short enough wavelength to cause fluorescence in some chemicals, in the same way as radiation further into the ultraviolet ('black light') does. Light of a shorter wavelength than 400 nm is classified as ultraviolet. Devices that employ blue laser light have applications in many areas ranging from optoelectronic data storage at high density to medical applications. Red lasers can be built on gallium arsenide (GaAs) semiconductors, upon which a dozen layers of atoms are placed to form the part of the laser that generates light from quantum wells. Using methods similar to those developed for silicon, the substrate can be built free of the defects called dislocations, and the atoms laid down so the distance between the ones making up the ground and those of the quantum wells are the same. However, the best semiconductor for blue lasers is gallium nitride (GaN) crystals, which are much harder to manufacture, requiring higher pressures and temperatures, similar to the ones that produce synthetic diamonds, and the use of high-pressure nitrogen gas. The technical problems seemed insurmountable, so researchers since the 1960s have sought to deposit GaN on a base of readily available sapphire. But a mismatch between the structures of sapphire and gallium nitride created too many defects. In 1992 Japanese inventor Shuji Nakamura invented the first efficient blue LED, and four years later, the first blue laser. Nakamura used the material deposited on the sapphire substrate, although the number of defects remained too high (106–1010/cm2) to easily build a high-power laser. In the early 1990s the Institute of High Pressure Physics at the Polish Academy of Sciences in Warsaw (Poland), under the leadership of Dr. Sylwester Porowski developed technology to create gallium nitride crystals with high structural quality and fewer than 100 defects per square centimeter — at least 10,000 times better than the best sapphire-supported crystal.